The emergence and popularity of mobile computing has made various types of portable electronic devices a staple in today's marketplace. In addition to mobile networking, many mobile devices are now equipped with the technological capabilities for enabling rich location-based services. For example, global positioning and compass sensors are often included in such devices for communicating the geographic location and the facing direction of the user, respectively. Furthermore, modern high-speed wireless networks are capable of delivering rich media in real-time. Due to the copious amount of information available on the interne, however, only a fraction of the available information can be presented to the user at any given time.